Solid state motor driven antenna rotator control circuit



P 1970 s. TIC'KNOR 3,527,993

SOLID STATE MOTOR DRIVEN ANTENNA ROTATOR CONTROL CIRCUIT Filed Feb. 12,1968 INVENTOR. SERGE] L. TICK/VCR BYWZW United States Patent Oflice3,527,993 Patented Sept. 8, 1970 3,527,993 SOLID STATE MOTOR DRIVENANTENNA ROTATOR CONTROL CIRCUIT Sergei L. Ticknor, Earlville, N.Y.,assignor, by mesne assignments, to Jerrold Electronics Corporation,Philadelphia, Pa., a corporation of Delaware Filed Feb. 12, 1968, Ser.No. 704,633 Int. Cl. G05b 11/12 U.S. Cl. 318-674 2 Claims ABSTRACT OFTHE DISCLOSURE An antenna rotational control system is provided having aconsole control comprising a variable potentiometer which is an arm of abridge, the other arm being coupled to the antenna. A solid statecontrol circuit including a DC motor and a stabilized dual SCR circuitdrives said antenna in response to position control positions on saidconsole.

My invention relates to an antenna rotator control circuit. Moreparticularly, it relates to a television antenna positioned on a rooftop, the direction of which may be operated by manual controls from acommand console inside the house.

The antenna rotator system must operate effectively over long periods oftime during the winter and surnmer. It is necessarily subjected to widetemperature variations as well as other environmental problems caused bywind, snow, rain and storms. It is desirable, therefore, to have anantenna rotator system which is simple and most reliable, and which willstand up over a long period of time.

Prior antenna rotator systems have utilized a motor which responds tothe imbalances in a bridge circuit. These systems have included relaysin control circuits to actuate and drive an AC motor in the respectivedesired directions. One of the common problems in such systems is thatthe relays themselves carry substantial currents and over a long periodof time arcing, wear and other mechanical problems have appeared.

An object of my invention is to provide an improved and reliable antennarotator motor control system.

A further object of my invention is to provide a' simple antenna rotatorcontrol system utilizing a DC motor.

Still another object of my invention is to provide an antenna rotatorsystem which does not require relays and eliminates the problem ofarcing and reduces the requirements of servicing.

Another object of my invention is to provide a console operated antennarotator system which inherently cannot lose synchronization.

Briefly, in my invention 1 provide an antenna otator system including aDC motor which responds to imbalances in a bridge circuit. When a personwishes to have the direction of the antenna changed, he provides amanual operation or command which alters the resistance ratio in one legof the bridge and thereby provides a voltage differential. Thisdifferential is picked up by the motor control system to drive the DCmotor which in'turn rotates the antenna. When the antenna rotates, theresistance ratio in the other leg of the bridge is varied in a directiontowards bridge equalization. When the antenna is pointed in the rightdirection, the bridge is balanced. In the preferred embodiment, themotor control comprises common cathode dual SCR circuits, the triggeringof which is caused by the bridge dilferential and provides the positiveor negative half cycles from the AC power supply to the DC motor tocause motor drive in either direction.

One of the advantages achieved with the elimination of relays is thatthe console operation is completely silent. The system is more reliablebecause there are no moving parts except for the potentiometers in thebridge circuits.

The DC motor operation requires lower amounts of power and results inessentially cooler operation. Because of the speed torque characteristicof the DC motor, the response is quicker and higher rotational speedsare achieved.

The above-mentioned and other features and objects of this invention andthe manner of attaining them will become more apparent and the inventionitself will be best uderstood by reference to the following descriptionof an embodiment of the invention taken in conjunction with theaccompanying drawing, wherein:

FIG. 1 is a circuit diagram illustrating my antenna rotator motorcontrol.

Referring now to FIG. 1, there is shown a motor M1 connected to a driveshown diagrammatically at 10. One side of M1 isgrounded. The drive 10 iscoupled to the antenna shown at 20 to cause it to move in accordancetherewith. In the embodiment shown, the drive 10 causes a ring torotate. The ring houses or contains the potentiometer resistance elementR2. The drive 10, when driven counterclockwise, causes clockwiserotation of R2 The antenna position detector comprises bridgepotentiometers R1 and R2 having respective wipers W1 and W2. If theposition of the wipers on the potentiometer is the same with respect toeach other, i.e., the resistance ratio formed thereby is the same, therewill be 0 volt between points 1 and 2. If there is a difference inmechanical positioning between W1 and W2, it will be indicated by avoltage proportional to this offset with a polarity indicating theoffset direction.

R1 is located in a unit, such as a console, inside the house. Wiper W1of potentiometer R1 may be manually operated to position the antenna inany desired direction.

A transformer T1 having a dual secondary S1 and S2 supplies power forthe operation of the SCR motor control circuit and the bridge circuit.

S1 is connected to a full wave bridge rectifier 30 having rectifiersCR5, CR6, CR7, CR8. This supplies DC for the bridge controlpotentiometers R1 and R2 at terminals 11, 12 and 21, 22.

The operation of the motor M1 is controlled by the voltages obtainedfrom the secondary S2. The AC voltage at S2 consists of a sine wavehaving positive and negative halves. In the operation of this system,either the positive halves of the signal or the negative halves of thevoltage signals are applied to the motor. When the positive half cyclesare applied, the motor is caused to rotate in one direction and when thenegative halves are applied, the voltage causes the motor to rotate inthe opposite direction.

The control circuit comprises an input resistor R3 coupled from wiper W2of potentiometer R2 and an input resistor R4 coupled from wiper W1 ofpotentiometer R1. A dual control rectifier circuit is employed havingSCR1 and SCR2, the cathodes being connected together. The gate electrodeof SCR2 is coupled to R4 and the anode of SCR2 is connected to the rightside r of the secondary S2. The gate electrode of SCR1 is coupled to R3while the anode of SCR1 is connected to the grounded side of the motorover 118. The other side of the motor is connected through a radiofrequency choke or inductor RFCl, and by conductor to the left side I ofthe secondary S2.

Series capacitors C2 and C3 are connected across from one gate electrodeto the other. Rectifier CR1 is connected between the gate and anode ofSCR1, and CR2,

biased in the same direction as CR1, is connected from.

of SCR2. CR4, biased in the same direction as CR3, is connected from thegate of SCR2 to the collector'of SCR2. Thus, if SCR2 is on, CR1 and CR2are conducting and SCRl is off; if SCRI is on, CR3 and CR4 areconducting and SCR2 is off.

When there is a voltage present at Rla and R2a, as a result of a consolecommand rotation of R1, it will be applied across the two SCR gateresistors R3 and R4. SCRl or SCR2 must have a positive gate to cathodevoltage (approximately .6 volt) to trigger the gate and cause conductionfrom cathode to anode.

When the wiper is moved easterly, as shown by the dotted lines, SCR2conducts during the half cycle when terminal r of the secondary of T1 ispositive, as indicated. The circuit is completed from the right side r,through SCR2, conductors 120, 116, 115 through CR2 and CR1, andconductor 118 to the common side of the motor. When CR2 conducts and CR3blocks, all the bridge output voltage appears across the gate andcathode of SCR2. If this is above the minimum gate trigger voltage (.6volt), SCR2 will conduct, allowing a positive path through SCR2, CR2 andCR1. Turning the antenna from T1 across the motor M1 causing it to run,turning the antenna. At this time, terminal 1 of S2 is negative and thenegative half cycle is applied over conductor 110 RFCl to the motor.This allows a half wave rectified voltage from T1 across the motor M1causing it to run, turning the antenna. The motor drives the antenna andthe potentiometer ring of the bridge 2 in a manner to compensate for theimbalance and in an easterly direction. When the antenna turns thepotentiometen'wiper W2 also moves towards its identical position with 1.When the differential voltages lowers to the trigger voltage (.6 volt)again, the SCR will drop out of conduction stopping antenna rotation bythe motor drive system.

A positive voltage appears across R3 when the wiper of potentiometer R1is moved westerly, as indicated by the dotted lines. SCRl then is turnedon during the half cycle when terminal r is negative causing a circuitto be completed from the right side of secondary S2 through CR4, CR3,connectors 115, 116 to SCRI, connectors 117, 118 to the grounded side ofthe motor; from the positive side of the motor through RFCI, connector110 to the left side of S2. Thus, when SCRl is on, motor terminal 120 ispositive relative to motor terminal 121 and when SCR2 is on, motorterminal 120 is relatively negative.

I have also provided certain protecting features. When SCR2 isconducting, CR1 and CR2 will have equal voltage drops of approximately.6 volt. This provides a negative bias across SCRl to protect it fromspurious triggering. C2 and C3 serve as a gate filter to reducetransients, which could cause unwanted triggering and provide astabilizing elfect.

RFCI and C4 compose an RF1 network which reduces R.F. interference above50 mHz. C1 reduces R.F. below 50 mHz. and reduces commutator ripplewhich can cause instability.

While the foregoing description .sets forth the prin ciples of theinvention in connection with specific apparatus, it is to be understoodthat this description is made only by way of example and not as alimitation of the scope of the invention as set forth in the objectsthereof and in the accompanying claims.

What is claimed is:

1. An antenna rotator control system comprising an antenna means, a DCmotor means, console power means to convert AC to DC, bridge meanscomprising first and second otentiometers, said console power includinga DC circuit applying DC to each of the otentiometers, said consolemeans including said first potentiometer and having a movable,positioning wiper, said second potentiometer having a stationary wiperand rotating means including a resistance element for said secondpotentiometer, said rotating means coupled to said antenna means forproviding rotational movement to said antenna means, solid state motorcontrol circuit means coupled to the respective wipers to determine andimbalance condition, said solid state motor control circuit means toapply positive or negative rectified AC respectively to said motor formoving said antenna means in a direction which is a function of thepolarity of the rectified AC, said console power means include an ACsource and first and second secondaries, said first secondary coupled tosaid DC circuit, whereby DC is applied to said potentiometers, saidmotor control circuit means applying, from the AC, supplied from saidsecond secondary, positive, or

negative half-cycles to the DC motor to cause respective rotation ineither direction, said solid state motor control means comprise dualcontrol SCR means, each having a gate, commonly connected cathodes andan anode electrode, means to couple the wipers of each potentiometer ofsaid bridge circuit means to said respective gate, stabilization andbiasing means for said dual control SCR means coupled to said wipersincluding first and second series rectifiers coupled across the anodeand cathode of the first of the dual SCR means with the commonconnection of said series rectifiers connected to said SCR gate, andthird and fourth series rectifiers connected in opposite seriesrelationship from said first and second rectifiers and across the secondSCR, with the common connection of said third and fourth rectifiersconnected to said second SCR gate, a pair of series capacitors coupledbetween the respective gates having their common terminal connected tothe common SCR cathode and the common terminal between the second andthird rectifiers, said second secondary being coupled to said motorthrough two paths, said first path including said second SCR and saidfirst and second rectifiers, said second path including said first SCRand. said third and fourth rectifiers, said paths coupling to oppositeterminals of said motor.

2. The system of claim 1 including radio frequency interferencesuppressing means coupled to said DC motor, whereby commutator ripplecaused by high radio frequencies may be reduced.

References Cited UNITED STATES PATENTS 3,327,186 6/1967 Gregory et al.3,329,945 7/ 1967 Deming. 3,355,640 11/1967 Lewis et al.

THOMAS E. LYNCH, Primary Examiner US. Cl. X.R. 318681

